The City of Chicago had several neighborhoods that could see Lake Michigan but had no way to access the lakefront safely. To quote Mayor Rahm Emmanuel, “For far too long, residents of this community could see the lakefront, but they couldn’t easily reach it.”
Two new serpentine pedestrian bridges were built to create access to Lake Michigan. One of these projects was the 41st Street Pedestrian Bridge.
This bridge crosses over South Lake Shore Drive and the Metra Electric/CN Railroads, creating a path to Lake Michigan. The new, 1,470-foot-long span incorporates twin 240-foot-long inclined arches on flowing S-Curves. This improves lakefront access on the south side. The bridge is aesthetically pleasing with its unique design. The 41st Street arch spans are on reverse curvature and on a long crest curve where the center between the arches is 7 feet higher than the outside ends of the arch at the approaches.
Lakefront access was the primary goal of this project, connecting the Bronzeville neighborhood with Lake Michigan. It is fully ADA accessible, with ramps to accommodate bicycles, wheelchairs, and emergency vehicles.
- 3D solids models for the thrust blocks. These were extremely irregular shapes that needed to be exact for anchor bolts and were used for volumes.
- 3D FG surface for the east and west sides of the bridge. This FG was created for the roads, ADA ramps, sidewalks, walls, and grading.
- 3D SG surface for the east and west sides. This was the most complicated part of the model due to six different types of depths that needed to be created for the different soil types.
- Bridge setup.
- Surveyed fabricated steel assemblies at an offsite facility to assist with field layout of thrust blocks and bolt patterns.
- Utilized designer’s 3D model to assist with real-time layout and placement of erected steel assemblies during overnight operations. As the steel was being placed in the air, Kapur selected a fixed point on the steel to use and to place X, Y, Z.
- Construction layout of landscaping, bridge, storm sewer, utilities, bike path, MSE walls, sidewalk, and ADA ramps.
A combination of quality design plans, an independent 3D model developed by the fabricator, and close coordination between the designer, construction engineer, and contractor resulted in a successful project.
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